Biological breeding method for cultivating high-yield early-maturing rice with characteristics of low temperature resistance and lodging resistance

Abstract

The invention discloses a biological breeding method for cultivating high-yield early-maturing rice with low-temperature-resistant and lodging-resistant characteristics by using a molecular recurrent assisted shuttle method. The method comprises the following steps: selecting parents which are resistant to cold, resistant to lodging and high in adaptability for multiple rounds of hybridization, screening cold-resistant and lodging-resistant strains by direct seeding in a Hainan winter (anti-season) group, carrying out stress identification in a Heilongjiang summer (in-season) cold water pool and a high-fertilizer field, and carrying out phenotype high selection pressure assisted by a genome information combined selection technology. And efficient polymerization of cold resistance, lodging resistance and high-yield and early-maturing characters is realized. According to the method, the technical bottleneck of insufficient multi-character collaborative improvement including cold resistance, disease resistance and lodging resistance in traditional early-maturing japonica rice breeding is solved, and the multi-character collaborative improvement breeding efficiency is remarkably improved. The vacant shell rate of the case variety Zhongnong japonica 5205 bred by the method is lower than 12.9% under low-temperature stress, the cold resistance is improved by more than 50% compared with that of parents, and the method has the characteristics of high yield, disease resistance and high quality.

Description

Technical Field

[0001] The present invention relates to a positive and negative season shuttle method assisted by molecular recurrent selection, a biological breeding method for cultivating high-yield and early-maturing rice with both low-temperature tolerance and lodging resistance characteristics, and belongs to the technical fields of crop genetic breeding and biological breeding. Background Technique

[0002] As an important commercial grain production base in China, the rice planting area and yield in the Heilongjiang rice region rank among the top in the country. Especially in the third and fourth accumulated temperature zones, due to the high-latitude geographical characteristics, strict requirements are put forward for the extremely low-temperature tolerance characteristics of rice varieties. At the same time, in recent years, the frequent occurrence of typhoons caused by global climate change has made the selection of rice lodging resistance performance also become a key goal of breeding work. However, there are many technical bottlenecks in the current selection of rice low-temperature tolerance and lodging resistance characteristics. First, the complexity and limitations of low-temperature tolerance identification: Rice cold damage runs through the germination period to the maturity period. Among them, the cold tolerance at the seedling stage, transplanting stage, tillering stage, booting stage, and flowering stage are mostly independent traits genetically and need to be identified separately. Among the existing identification methods, although the artificial climate chamber and water bath method are suitable for the identification of cold tolerance at the seedling stage, there are problems such as poor temperature uniformity, limited scale, and high environmental control costs; the cold water pool treatment and high-altitude identification are more suitable for the evaluation of cold tolerance during the reproductive growth period, but they are limited by insufficient treatment scale, large errors in the identification of materials at different maturity stages, and the ecological differences between the high-altitude environment and the Heilongjiang plain rice region make it difficult to directly apply the identification results. In addition, the two types of identification methods cannot replace each other, resulting in an extended breeding cycle and low efficiency. Second, the problem of high-throughput screening for lodging resistance identification: Traditional lodging resistance identification relies on methods such as measuring the breaking force of the stem and detecting the lodging resistance stress. Although it can accurately evaluate the lodging resistance performance of a single plant, the operation is cumbersome and the throughput is low, making it difficult to meet the screening needs of large-scale breeding populations. Typhoons frequently occur in the Heilongjiang rice region, putting forward higher requirements for the rapid identification of the lodging resistance ability of varieties at the adult stage. Therefore, there is an urgent need for an efficient screening system that combines environmental stress and phenotypic observation.

[0003] In the prior art, the single phenotype identification method is limited by environmental differences (such as the differences in climate and soil between the off-season identification in Hainan and the normal-season environment in Heilongjiang), resulting in deviations in the genotype-phenotype association analysis of cold tolerance and lodging resistance. For example, the differences in temperature and light conditions between the southern environment at high-altitude identification sites and the Heilongjiang Plain may obscure the true genetic effects of target traits; it is difficult to simulate multi-factor stresses in the field (such as low temperature accompanied by pests and diseases, and fertility differences) in the small environment control of artificial climate chambers, affecting the reliability of the identification results. With the development of technologies such as genomic selection and marker-assisted breeding, it has become possible to efficiently aggregate multiple target traits such as cold tolerance, lodging resistance, and high yield. However, the existing methods have not yet formed a mature technical system: on the one hand, the mapping and marker development of cold tolerance and lodging resistance genes require the combination of large-scale segregating populations and multi-environment phenotype data; on the other hand, in traditional shuttle breeding between seasons, the precise stress treatments of natural low-temperature stress in the off-season identification in Hainan and cold water ponds and high-fertilizer fields in the normal season in Heilongjiang urgently need to be deeply integrated with genomic selection technology to break through environmental limitations and improve the screening efficiency of excellent genotypes.

[0004] Therefore, there are significant deficiencies in the prior art in terms of the identification methods for low-temperature tolerance and lodging resistance characteristics, the aggregation efficiency of multiple target traits, and the screening of environmental adaptability. The present invention constructs a set of highly efficient and collaborative biological breeding systems through the integrated innovation of molecular recurrent aggregation, shuttle screening between seasons, and genomic selection technology, effectively solving the technical problems of the coordinated improvement of low-temperature tolerance and lodging resistance characteristics in the breeding of high-yield and early-maturing rice varieties in the Heilongjiang rice region. Summary of the Invention

[0005] Aiming at the deficiencies of the above prior art, the present invention aims to provide a biological breeding method for cultivating high-yield and early-maturing rice with low-temperature tolerance and lodging resistance characteristics, realizing the directional cultivation of rice varieties with low-temperature tolerance, lodging resistance, high yield, and early maturity. Breaking through the limitations of the existing single phenotype identification method, it is an efficient biological breeding method integrating molecular recurrent aggregation, shuttle screening between seasons, and genomic selection technology.

[0006] To achieve the above object, the present invention adopts the following technical solutions: The present invention provides a biological breeding method for cultivating high-yield and early-maturing rice with cold tolerance and lodging resistance characteristics, comprising the following steps: (1) Molecular recurrent assisted polymerization: Select high-yield breeding materials (breeding material 1) carrying high-yield, cold tolerance and disease resistance characteristics, and breeding materials (breeding material 2) carrying high-yield and lodging resistance characteristics as male parents, and use early-maturing varieties / lines with excellent adaptability in the target area as bridge parents to conduct two rounds of hybridization to obtain polymerization hybrid seeds; (2) Off-season screening / identification: In winter in Hainan, the segregating generation materials are planted by thin direct seeding, and the stable generation materials are planted by transplanting seedlings after staged sowing, and screening is carried out in combination with the phenotypic investigation of the seed setting rate under low-temperature and strong selection pressure stress and the field performance of lodging resistance; (3) Main-season identification / screening: In summer in Heilongjiang, the materials are identified for high-yielding ability, cold tolerance under strong cold water selection pressure stress, lodging resistance and disease resistance in high-fertilizer fields, rice quality and variety comparison; (4) Genome information assisted selection: Based on the parental genome sequencing and molecular marker development, genetic information related to target traits is obtained to assist in screening excellent offspring.

[0007] In one embodiment, the present invention further includes that the breeding material 1 is Zhongnongjing 18 carrying disease resistance and cold tolerance characteristics, the breeding material 2 is Zhongnongjing 11 carrying lodging resistance characteristics, and the bridge parent is the early-maturing excellent variety Longping 386 with good adaptability in the target area.

[0008] In another embodiment, the present invention further includes that the two rounds of hybridization are specifically as follows: In the first round of hybridization, the cold tolerance and disease resistance variety and the high-yield and lodging resistance variety are respectively hybridized with the bridge parent to obtain F1 generation seeds; In the second round of hybridization in Hainan, the two F1 generations are hybridized, and no less than 1000 polymerization hybrid seeds are harvested.

[0009] In another embodiment, the present invention further includes that in the off-season screening / identification, when the segregating generation materials are planted by thin direct seeding, the seeding rate per mu is 8-10 catties, sown on the seedbed, and the cold water stress conditions are water temperature ≤ 17°C and water depth 20 cm for 7-20 days.

[0010] In another embodiment, the present invention further includes that in step (3), the nitrogen fertilizer application rate in the high-fertilizer field is increased by 30% compared with the conventional field, and the disease is artificially induced by soaking the susceptible rice straw in the liquid.

[0011] In another embodiment, the present invention further includes that the genome selection in step (4) includes: Genotype analysis of parents and recombinant inbred line populations is carried out by combining third-generation sequencing and liquid-phase chip; Offspring are screened based on haplotype markers of cold tolerance genes and lodging resistance genes.

[0012] In another embodiment, the present invention further includes that in the off-season screening / identification, the one-season two-generation selection is specifically as follows: In the first generation, single ears are selected from the direct seeding group, in the second generation, ear rows are selected from the ear line direct seeding, and the selected ear rows are planted in single plants in Heilongjiang, and excellent single plants are selected in combination with the maturity period and added generation in Hainan.

[0013] In another embodiment, the present invention further includes that in the cold water stress screening, at the maturity stage, the seed setting rate is used as the cold tolerance identification index, and the discrimination method under low temperature stress is the same as that in the off-season screening, and all the ears of the plant holes with the highest seed setting rate are harvested.

[0014] In another embodiment, the present invention further includes that in the disease resistance and lodging resistance screening, the disease-susceptible induced materials are sprayed by soaking the extract of the previous season's rice straw to increase the incidence of disease, and the disease resistance is investigated at the tillering stage and the maturity stage respectively, and the lodging situation is investigated at the maturity stage.

[0015] In another embodiment, the present invention further includes that the genomic selection is specifically as follows: performing three-generation genomic sequencing on high-yield cold-tolerant disease-resistant, high-yield lodging-resistant parents and bridge parents, developing polymorphic molecular markers, constructing genetic information of cold tolerance and lodging resistance traits based on segregating populations, and combining genome-wide marker-assisted screening of offspring individuals / lines.

[0016] Beneficial effects achieved by the present invention: (1) The present invention realizes the efficient aggregation of multiple traits: through two rounds of pyramiding hybridization and molecular recurrent selection, the directional recombination of cold tolerance, lodging resistance, high yield, and early maturity genes is realized. The cold tolerance of the offspring materials (empty shell rate ≤ 12.9%) is improved by more than 50% compared with the parents (Table 1), the lodging resistance index ≤ 25%, and the growth period is shortened by 5 - 7 days compared with the control.

[0017] (2) The present invention conducts environmental adaptability screening: the coordinated stress identification of natural low temperature in the off-season in Hainan and cold water ponds and high-fertilizer fields in the main season in Heilongjiang simulates the real environmental pressure in the target area, solves the environmental deviation problem of traditional identification methods, and improves the screening accuracy.

[0018] (3) The breeding efficiency of the present invention is significantly improved: one-season two-generation direct seeding for generation addition (completing two generations of screening in a single season in Hainan) combined with genomic selection technology shortens the traditional breeding cycle by 2 - 3 years, increases the screening throughput by more than 30%, and significantly reduces the breeding cost.

[0019] (4) The present invention coordinately improves the quality of rice: through multi-environment rice quality identification, it ensures that the developed varieties meet the national standards of processing quality, appearance quality, and eating quality at the same time, and realizes the coordinated improvement of yield, resistance, and quality.

[0020] In summary, the present invention constructs an integrated breeding technology system of "molecular design - environmental stress screening - genomic precise selection", provides an efficient solution for the coordinated improvement of multiple target traits in cold rice regions, and the developed varieties can be directly applied to the third and fourth accumulated temperature regions of Heilongjiang, promoting the sustainable development of the rice industry in response to climate change. Description of the Drawings

[0021] Figure 1Technical roadmap of the breeding method involved in the present invention.

[0022] Figure 2 Process of breeding the high-yield and early-maturing line Zhongnongjing 5205 with both cold tolerance and lodging resistance by using the breeding method of the present invention.

[0023] Figure 3 Field growth vigor of direct-seeded fields and field performance of cold tolerance at the adult stage.

[0024] Figure 4 Yield identification performance of transplanted fields.

[0025] Figure 5 Identification of major cold-tolerant genes and haplotype analysis. Specific implementation manners

[0026] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited by the embodiments.

[0027] The experimental materials, reagents, instruments and methods used in the following embodiments, unless otherwise specified, are all conventional experimental materials, reagents, instruments and methods in the art and can be obtained through commercial channels. The experimental materials used in the embodiments: Zhongnongjing 18 and Longping 386 are both approved varieties, and Zhongnongjing 11 is participating in the experiment and can be obtained through public channels. The technical roadmap of the breeding method involved in the present invention is as Figure 1 shown.

[0028] Example 1 Parent selection and molecular recurrent pyramiding hybridization (1) Parent selection Cold-tolerant and disease-resistant male parent: Select the advanced backcross introgression line variety "Zhongnongjing 18", which is approved in the third accumulated temperature zone of Heilongjiang. After identification, it has strong cold tolerance during the reproductive growth period (the empty shell rate under outdoor low-temperature treatment is 20.52%, Table 1) and carries the major cold-tolerant gene.

[0029] Lodging-resistant male parent: Select the advanced backcross introgression line variety "Zhongnongjing 11", which has the characteristics of high yield, strong stem breaking resistance and carries the lodging-resistant gene.

[0030] Bridge parent: Select the adaptable early-maturing variety "Longping 386", which is an early-maturing excellent variety with good adaptability in the target area.

[0031] Table 1 Cold tolerance performance of parents Zhongnongjing 11, Zhongnongjing 18 and their offspring Zhongnongjing 5205 under standard cold tolerance identification conditions

[0032] (2)Two rounds of pyramiding hybridization The first round of hybridization: Prepare hybridization combinations respectively; harvest sufficient hybridization seeds.

[0033] Hybridize "Zhongnongjing 18" with "Longping 386" to obtain cold-tolerant and early-maturing F1 generation seeds (denoted as A); Hybridize "Zhongnongjing 11" with "Longping 386" to obtain lodging-resistant and early-maturing F1 generation seeds (denoted as B); Harvest F1 seeds by single plant, and each combination harvests ≥500 seeds.

[0034] Second round of hybridization: In Hainan, conduct polymerization hybridization with the two F1s, and harvest more than 1000 sufficient hybrid seeds.

[0035] To analyze the genetic mechanisms of cold tolerance, disease resistance and lodging resistance, configure reciprocal cross F1 of Zhongnongjing 18 / Zhongnongjing 11, and derive two sets of recombinant inbred line (RIL) populations through single-seed descent, with each population maintaining about 200 random plant lines ( Figure 2 as shown in the molecular recurrent polymerization part).

[0036] Example 2 Screening in the off-season in Hainan and selection in two generations in one season According to the perennial meteorological data, the low temperature below 14 degrees usually appears around the Spring Festival in winter in Hainan; according to practical observations, the flowering period of northern japonica rice will be extended for a long time during the winter in Hainan for southward breeding. The heading dates between different tillers of the same single plant will be concentrated within 5 days in the north, while in winter in Hainan, they will differ by more than 10 days, which sharply increases the possibility of the same breeding material encountering low temperature. Utilizing these two characteristics, we can screen / identify the cold tolerance and lodging resistance characteristics of breeding materials in winter in Hainan, mainly through direct seeding group screening and supplemented by stable material / plant line identification. The specific operations are as follows: 2.1 Material planting According to different identification purposes, for stable generation materials including parents, adopt the planting method of sowing seedlings at different times and transplanting; for segregating generation materials, adopt the sparse direct seeding method, specifically as follows: 1) Transplanting planting Considering the growth duration from sowing to heading and the expected harvest time of materials in Heilongjiang, usually sow in late October for the first batch, with an interval of about 10 - 15 days, and continuously sow 2 - 3 periods. Transplant the materials with single-plant planting, and plant the production control of the same sowing date around. If it is a hybrid, plant the female parent in front of the material. Combine phenotypic and genomic marker identification to remove pseudo-hybrids or mixed seeds. Compare and apply more tiller fertilizers and panicle fertilizers under normal field management levels, applying more than 20 kg of compound fertilizer per mu to increase the growth amount, tiller number and number of grains per panicle, so as to extend the time interval between the first heading spike and the last heading spike of each single plant of each material, and between the top florets and the basal florets of each panicle as much as possible, so that the material can effectively encounter low temperature stress.

[0037] 2) Sparse direct seeding planting Adopt the sparse direct seeding method. According to the actual production situation, the seeding rate per mu is 8 - 10 catties. Calculate the seeding rate for each material and sow it on a seedbed about 1 meter wide. Each material is sown in a length of about 4 meters. Set up direct seeding of the production control variety at the head, middle, and tail of the seedbed for three consecutive plots. Considering that the materials from Heilongjiang mature earlier in Hainan, the field fertilizer application should be appropriately increased, which can also be beneficial for the lodging resistance screening. If adding two generations in one season, the sowing time is set before the sowing of the first-generation transplanting materials, and it is advisable to be in early October. Then, generally, the possibility of encountering low temperature during the reproductive growth period of the first generation (December) is smaller than that of the second generation (February). At this time, the cold tolerance selection of the second generation should be emphasized.

[0038] 2.2 Discrimination of materials under low-temperature stress and screening for cold tolerance and lodging resistance Refer to the production control planted in adjacent fields during the same period, and make the following further distinctions according to the seed setting situation of different individual plants of each material: 1) If the seed setting situations of all tillers of the whole individual plant are similar and all are poor, further observe the same material at different stages. If the situation is similar, then it can be preliminarily determined that it is related to the characteristics of the material itself, such as hybrid sterility caused by distant hybridization, etc.; 2) On the contrary, if there are significant differences in the seed setting situations among different tillers of the whole individual plant or there are significant differences in the seed setting rates of the same material at different stages, combined with the meteorological data during the young panicle differentiation period of the current season, the materials suffering from low-temperature cold damage stress can be preliminarily discriminated (as shown in Figure 3 ); 3) Select the critical period, that is, the period when the normal grains of the ears of different batches suffering from low-temperature stress are yellow and ripe while the empty and shriveled grains are green, from after the low temperature in spring festival to before maturity, and conduct field investigations, usually for 2 - 3 rounds; 4) For the materials determined to be suffering from low-temperature cold damage stress, select the ear with the worst seed setting, count the seed setting rate, and identify the cold tolerance of the material.

[0039] 5) Refer to the adjacent control, and conduct lodging resistance screening according to the later lodging performance of the direct seeding group. It should be noted that there are pests such as planthoppers in Hainan, so timely investigations should be carried out to exclude the influence of pest damage and other factors.

[0040] 2.3 Selection for two generations in one season In Hainan, conduct direct seeding for two generations in one season. Select single ears from the first-generation group and select ear rows from the second-generation ear line direct seeding. The selection rate does not exceed 5%. The selected ear rows are planted in single plants in Heilongjiang, observe the comprehensive agronomic traits, and strictly conduct maturity selection with reference to the control. Select excellent single plants from the selected plant lines, add generations in Hainan, and continue to observe the winter seed setting rate.

[0041] Example 3 Positive-season identification in Heilongjiang and multi-environment screening 1. Yield potential selection In the normal fields of transplanted rice sown in the main season in Heilongjiang, select individual plants with good high-yielding characteristics, and control the selection rate at about 10%. Harvest all the seeds of each individual plant separately. Next, in the main seasons of the following two consecutive years, conduct plot planting of the selected excellent individual plants in Heilongjiang, and carry out cross screening and identification under stress conditions.

[0042] 2. Cold water stress screening Transplant in clusters in the cold water pond, plant production controls at certain intervals. Considering that cold water stress will affect the growth amount, appropriately increase the nitrogen fertilizer in the conventional fields of the cold water pond. From the full tillering stage to before the young panicle differentiation, use cold water below 17 °C, with a water depth of about 20 cm to submerge the auricles of the flag leaves, and continue for 7 - 20 days, then resume normal irrigation. At maturity, use the seed setting rate as the index for screening and cold tolerance identification. Specific discriminant and identification indicators for low-temperature stress: Han Longzhi, Zhang Sanyuan. Identification and evaluation methods for cold tolerance of rice [J]. Journal of Plant Genetic Resources, 2004(01): 75 - 80. Refer to the production control in the adjacent fields, select the materials that have withstood cold water stress and have a seed setting rate not lower than the control, and harvest all the panicles of the hill with the highest seed setting rate.

[0043] 3. Disease resistance and lodging resistance screening Transplant in clusters in the high-fertilizer and disease fields, and increase the nitrogen fertilizer level by more than 30% compared with the normal fields; plant production controls and disease-susceptible induction materials at certain intervals. From the full tillering stage to before the young panicle differentiation, compare with the adjacent normal fields, and appropriately supplement fertilizers if the growth amount is insufficient. Use the straw of the disease-susceptible induction materials collected in the previous season, soak it and spray it on the disease-susceptible induction materials of the current year to increase the incidence of diseases.

[0044] Investigate the disease incidence at the tillering stage and maturity respectively; investigate the lodging situation of the materials at maturity. Select the materials with medium disease resistance and lodging resistance.

[0045] 4. Grain quality screening and identification Collect grain samples from the cold water pond, high-fertilizer and disease fields, and conventional fields respectively, and refer to the national standard "High-quality Paddy" to identify the rice quality including appearance quality, processing quality and eating quality.

[0046] 5. Variety comparison and identification Refer to the "Heilongjiang Provincial Regional Test Standard", and conduct variety comparison and identification under transplanting conditions (as Figure 4 shown) for the advanced-generation stable materials selected through the above process, and set up experimental replicates and controls.

[0047] Example 4 Genome selection and molecular marker-assisted screening Using third-generation sequencing combined with second-generation sequencing, extract the genomic information of the three cold tolerance and high-yield parents Zhongnongjing 18, lodging resistance and high-yield parent Zhongnongjing 11, and bridging parent Longping 386.

[0048] Using high-throughput genotyping methods such as 40K liquid-phase chips, genotype analysis was performed on the constructed reciprocal RIL population of Zhongnongjing 18 / Zhongnongjing 11. Combining multi-year and multi-point phenotypic identification, genomic dissection of cold tolerance, disease resistance, and lodging resistance characteristics was carried out. Molecular markers were developed for known important loci, and molecular marker-assisted identification of offspring was performed. Among them, the favorable alleles for cold tolerance mainly came from Zhongnongjing 18, the favorable alleles for lodging resistance mainly came from Zhongnongjing 11, and the favorable alleles for early maturity characteristics mainly came from the bridging parent Longping 386.

[0049] For genomic identification of excellent progeny of polymerization crosses, a genome sequencing method combining third-generation and second-generation sequencing can be used. The obtained genomic information is compared with the three parents to obtain their pedigree sources, especially the donor information for cold tolerance, disease resistance, and lodging resistance. On this basis, combined with the mapping results of the RIL population, the formation mechanisms of cold tolerance, disease resistance, and lodging resistance of excellent progeny of polymerization crosses are screened and analyzed (see Figure 5 ).

[0050] Through the combined application of the above methods, a high-yield and early-maturing variety Zhongnongjing 5205 with characteristics of cold tolerance, disease resistance, and lodging resistance was bred, and the empty hull rate of the treatment was less than 12.9%. The increase rate of cold tolerance seed setting rate compared with the parent Zhongnongjing 11 was more than 50% (as shown in Table 1).

[0051] Through the coordinated application of molecular recurrent polymerization, reciprocal-season shuttle screening, and genomic selection, the present invention successfully cultivated the rice variety "Zhongnongjing 5205" with characteristics of cold tolerance (empty hull rate ≤ 12.9%), lodging resistance (lodging index ≤ 25%), high yield (yield increase ≥ 5%), and early maturity (growth period shortened by 5 - 7 days). Its key characteristics are all superior to those of the parents and control varieties, verifying the efficiency and feasibility of this breeding method.

[0052] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with this technology can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A biological breeding method for cultivating high-yield and early-maturing rice with low-temperature tolerance and lodging resistance characteristics, characterized in that, It includes the following steps: (1) Molecular recurrent-assisted polymerization: Select high-yielding cold-tolerant and disease-resistant varieties and high-yielding lodging-resistant varieties as male parents, and use early-maturing varieties with excellent adaptability in the target area as bridging parents to conduct two rounds of hybridization to obtain polymerization hybrid seeds; (2) Off-season screening / identification: In winter in Hainan, the materials in the segregating generations are planted by sparse direct seeding, and the materials in the stable generations are planted by transplanting seedlings sown at different times. Screening is carried out by combining the phenotypic investigation of the seed setting rate under low-temperature strong selection pressure and the field performance of lodging resistance; (3) In-season identification / screening: In summer in Heilongjiang, the materials are identified for high-yielding ability, cold tolerance under strong cold water selection pressure, lodging resistance and disease resistance in high-fertilizer fields, rice quality and variety comparison; (4) Genome information-assisted selection: Based on parental genome sequencing and molecular marker development, genetic information related to target traits is obtained to assist in screening excellent offspring.

2. The biological breeding method according to claim 1, characterized in that, The breeding material carrying the high-yielding, cold-tolerant and disease-resistant characteristics is named breeding material 1, the breeding material carrying the high-yielding and lodging-resistant characteristics is named breeding material 2, and the bridging parent is a variety or line carrying excellent early-maturing characteristics and having good adaptability in the target area.

3. The biological breeding method according to claim 2, characterized in that, The two rounds of hybridization are specifically as follows: In the first round of hybridization, breeding material 1 and breeding material 2 are respectively hybridized with the bridging parent to obtain F1 generation seeds; in the second round of hybridization in Hainan, the two F1 generations are hybridized, and no less than 1000 polymerization hybrid seeds are harvested.

4. The biological breeding method according to claim 3, characterized in that, In the off-season screening / identification, when the materials in the segregating generations are planted by sparse direct seeding, the seeding rate per mu is 8-10 catties, sown in the seedbed, and the cold water stress conditions are water temperature ≤ 17°C and water depth 20 cm for 7-20 days.

5. The biological breeding method according to claim 4, characterized in that In step (3), the nitrogen fertilizer application rate in the high-fertilizer field is increased by 30% compared with the conventional field, and diseases are artificially induced by soaking the diseased rice straw extract.

6. The biological breeding method according to claim 5, characterized in that, The genome selection in step (4) includes: Genotype analysis of parents and recombinant inbred line populations is carried out by combining third-generation sequencing and liquid-phase chips; offspring are screened based on haplotype markers of cold-tolerant genes and lodging-resistant genes.

7. The biological breeding method according to claim 6, characterized in that In the off-season screening / identification, the one-season two-generation selection is specifically as follows: In the first generation, select single ears from the direct-seeding group, in the second generation, select ear rows from the ear line direct seeding, and the selected ear rows are planted in single plants in Heilongjiang, and excellent single plants are selected for additional generations in Hainan in combination with the maturity period.

8. The biological breeding method according to claim 7, characterized in that In the cold water stress screening, the seed setting rate is used as the cold tolerance identification index at maturity, and the discrimination method under low-temperature stress is the same as that in the off-season screening. All the ears of the plant holes with the highest seed setting rate are harvested.

9. The biological breeding method according to claim 8, wherein In the disease resistance and lodging resistance screening, the disease-susceptible induced materials are sprayed with the extract of soaking the rice straw of the previous season to increase the disease incidence. The disease resistance is investigated at the tillering stage and the maturity stage respectively, and the lodging situation is investigated at the maturity stage.

10. The biological breeding method according to claim 9, wherein, The genome selection is specifically as follows: Third-generation genome sequencing is carried out on the high-yielding, cold-tolerant and disease-resistant, high-yielding and lodging-resistant parents and the bridging parent to develop polymorphic molecular markers. Based on the segregating population, genetic information on cold tolerance and lodging resistance traits is obtained, and offspring individuals / lines are screened in combination with whole-genome marker-assisted selection.

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